1. Field of the Invention
The present invention relates generally to fluoropolymers and thermosetting compositions containing fluoropolymers. More specifically, the present invention is directed to fluoropolymers containing functional groups and thermosetting compositions that contain functional fluoropolymers.
2. Description of Related Art
Coatings derived from compositions containing fluoropolymers typically provide good chemical resistance, weather resistance, and heat resistance. Due to these properties, interest in using fluoropolymer-based paints has increased in various areas. For example, fluoropolymer-containing paints are used as weather resistant paints in the areas of architecture, automobile, and chemical engineering. The fluoropolymers used in such paints typically include a fluorocarbon monomer, such as chlorotrifluoroethylene, tetrafluoroethylene, or vinylidene fluoride, and another monomer, such as a vinyl ester or a vinyl ether, usually added to increase the solubility of the resulting fluoropolymer.
As an example, U.S. Pat. No. 4,345,057 to Yamabe et al. discloses a fluoropolymer having improved curing properties. Coatings using the fluoropolymer reportedly have a glossy finish, good chemical resistance, and good weatherability.
In many cases, the durability of a coating, such as its weatherability and/or chemical resistance, will depend on obtaining an optimum balance of physical properties, such as the hardness and flexibility of a coating film. Generally speaking, obtaining this optimum balance has been an elusive goal.
Moreover, the use of fluoropolymer-containing coating compositions has been limited due to the high cost of such coatings, due in part to the cost of the fluorocarbon monomers.
Functional fluoropolymers are typically random copolymers that include functional group-containing acrylic and/or methacrylic monomers. Such a functional fluoropolymer will contain a mixture of polymer molecules having varying individual functional equivalent weights and polymer chain structures. In such a copolymer, the functional groups are located randomly along the polymer chain. Moreover, the number of functional groups is not divided equally among the polymer molecules, such that some polymer molecules may actually be free of functionality.
In a thermosetting composition, the formation of a three-dimensional crosslinked network is dependent on the functional equivalent weight as well as the architecture of the individual polymer molecules that comprise it. Polymer molecules having little or no reactive functionality (or having functional groups that are unlikely to participate in crosslinking reactions due to their locations along the polymer chain) will contribute little or nothing to the formation of the three-dimensional crosslinked network, resulting in decreased crosslink density and less than optimum physical properties of the finally formed thermoset coating.
It would be desirable to develop fluoropolymer based thermosetting compositions that are low cost, have a predictable polymer architecture and provide an optimum balance of film hardness and flexibility in a durable coating.
The present invention is directed to a composition that includes a fluorine-containing copolymer containing at least 30 mol % of residues having the following alternating structural unit:
xe2x80x94[DMxe2x80x94AM]xe2x80x94
where DM represents a residue from a donor monomer having the following structure (I): 
where R1 is linear or branched C1 to C4 alkyl; R2 is selected from methyl, linear, cyclic or branched C1 to C20 alkyl, alkenyl, aryl, alkaryl, and aralkyl; and AM represents an acceptor monomer. The copolymer contains at least 5 wt. % fluorine.
The present invention is also directed to a composition that includes the copolymer described above, where the composition contains co-reactive functional groups. A non-limiting example of such a composition is a thermosetting composition. The present invention is also directed to a substrate, where at least a portion of the substrate is coated with the thermosetting composition.
The present invention is further directed to a thermosetting composition that includes the copolymer described above, containing reactive functional groups and at least one other component that contains functional groups that are reactive with the functional groups of the copolymer. The present invention is additionally directed to a substrate, where at least a portion of the substrate is coated with the thermosetting composition.
The present invention is still further directed to a multi-component composite coating composition that includes a base coat deposited from a pigmented film-forming composition and a substantially pigment free top coat applied over at least a portion of the base coat. The base coat and/or the top coat include one of the thermosetting compositions described above. The present invention is also directed to substrates where at least a portion of the substrate is coated with the multi-component composite coating composition.